Often large shafts such as hydraulic pistons are damaged in relatively small areas, such as by impact, bearing seizure, etc. In the past, it has been necessary to remove such shafts and transport them to a machine shop for repair. The shaft would have grooved, indented or otherwise damaged surface corrected by adding metal to the damaged area by electroplating, adding weld metal, etc. Then the shaft would need to be mounted in a large stationary centerless grinder or lathe so that the damaged area could be reformed to the original shape. The shaft would then need to be returned to the vehicle repair shop for remounting.
Similar repair sequences are necessary where the interior of a large metal cylinder or a large flat metal surface is damaged. This repair sequence is expensive, time consuming and results in long vehicle or other apparatus down time.
A number of different devices have been developed for grinding metal objects, such as ice skate blades or the like without removing the part to be ground from the overall device. Typical of these are the chamfering or deburring tool described by Seidenfaden in U.S. Pat. No. 4,504,178 and skate sharpening devices such as described by Wurthman in U.S. Pat. No. 5,591,069. While effective for their intended purposes, these devices are not adaptable to grinding of repaired surfaces such as large shafts, internal cylinders, etc.
Shafts having bends that prevent them from being turned or ground in a conventional lathe or stationary grinder can be ground in a machine that can revolve around a part, rather than rotating the part itself, as described by Ekholm et al. in U.S. Pat. No. 2,086,492. However, this requires the movement of the entire grinding apparatus around a relatively thin shaft and is not useful in grinding large shafts and the like.
Thus, there is a continuing need for a portable, hand held, grinding assembly for grinding and finishing large shafts, the interior of large cylinders on site, that can be operated on-site and does not requiring transporting a part to be repaired to a central repair facility and that is adaptable to grinding of large shafts, large internal cylinders and large planar surfaces.